<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>计数器</title>
</head>

<body>
    <!-- html结构 -->
    <div id="app">
        <!-- 计数器功能区域 -->
        <div class="input-num">
            <button @click="sub">
                -
            </button>
            <span>{{num}}</span>
            <button @click="add">
                +
            </button>
        </div>

    </div>
    <!-- 开发环境版本，包含了有帮助的命令行警告 -->
    <script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.js"></script>
    <!-- 编码 -->
    <script>
        var app = new Vue({
            el: "#app",
             data:{
                 num:1
             },
             methods:{
                 add:function(){                    
                    //  console.log('add');
                    if(this.num<10){
                        this.num++;
                    }
                   else{
                       alert('别点啦，最大啦！');
                   }
                 },
                 sub:function(){      
                     if(this.num>0)            
                    //  console.log('sub')
                    this.num--;
                    else{
                        alert('别点啦，最小了！');
                    }
                 }
             }
        })
    </script>
</body>

</html>